linux-kernel - Re: [patch 11/14] vfs: move executable checking into ->permission()

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Message-Id: <E1JzTwx-0001bw-DT@pomaz-ex.szeredi.hu>
Date:	Fri, 23 May 2008 11:52:35 +0200
From:	Miklos Szeredi <miklos@...redi.hu>
To:	hch@...radead.org
CC:	miklos@...redi.hu, linux-fsdevel@...r.kernel.org,
	hch@...radead.org, viro@...IV.linux.org.uk,
	linux-kernel@...r.kernel.org
Subject: Re: [patch 11/14] vfs: move executable checking into ->permission()

> > From: Miklos Szeredi <mszeredi@...e.cz>
> > 
> > For execute permission on a regular files we need to check if file has
> > any execute bits at all, regardless of capabilites.
> > 
> > This check is normally performed by generic_permission() but was also
> > added to the case when the filesystem defines its own ->permission()
> > method.  In the latter case the filesystem should be responsible for
> > performing this check.
> > 
> > So create a helper function exec_permission() that checks returns
> > -EACCESS if MAY_EXEC is present, the inode is a regular file and no
> > execute bits are present in inode->i_mode.
> > 
> > Call this function from filesystems which don't call
> > generic_permission() from their ->permission() methods and which
> > aren't already performing this check.  Also remove the check from
> > dentry_permission().
> > 
> > The new code should be equivalent to the old.
> 
> There's no point moving this into the filesystem.

Yes, there is.  Fuse already has special code, because it need to
refresh the attributes first before doing the "are there any x bits in
mode?" check.  And because there's some duplication, I've introduced a
helper.  That's exactly how we handle this sort of thing.

Miklos
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